1. Field of the Invention
The present invention relates to an oil passage structure for returning oil in an engine. A plurality of cylinder bores with substantially horizontal axes are lined up at cylinder blocks. A plurality of combustion chambers individually corresponding to each cylinder bore are formed between pistons fitted in a freely slidable manner into each cylinder bore and cylinder heads. Cam shafts interlocking with and coupled to a plurality of intake valves and a plurality of exhaust valves controlling intake of air to and exhaust emissions from the combustion chambers are positioned within valve chambers formed between the cylinder heads and head covers coupled to the cylinder heads. Furthermore, transmission mechanisms for reducing the rotational force of the crankshaft by half for transmission to the camshafts are provided between the crankshaft to which the pistons are commonly coupled at the crank chamber within the crankcases coupled to the cylinder blocks and the camshafts. More particularly, the present invention relates to an oil passage structure for returning oil from a valve chamber to a crank chamber.
2. Description of Related Art
Conventionally, as disclosed in, for example, Utility Model Laid-open Publication No. Sho. 63-65811, an oil passage for returning oil is typically provided in a cylinder head and cylinder block of an engine.
In the related art, a dedicated oil passage for returning oil is provided in the cylinder block and cylinder head. The cylinder block and cylinder head therefore become larger as a result of space being provided to position this oil passage for returning oil. Furthermore, the weight of the engine is increased.